Conventional shock absorbers have been utilized for decades to control the suspension, vibration, and smoothness of operation of automobiles, trucks, and similar motor vehicles. Conventional shock absorbers typically operate with the use of telescoping cylinders which utilize hydraulic or pneumatic pressure to control the extension and tension of the shock absorber so as to dampen and control the movement and oscillation of the struts, the large springs used to suspend the chassis. In operation, a piston associated with a first cylinder moves into and out of an oil-filled casing in response to the movements and vibrations of the vehicle. The downward thrust of the piston forces oil through a passage and valve located at the opposite end of the cylinder and into an outer sleeve. When the strut is thrust downward, the movement is only slightly dampened, so as not to impair the spring action of the strut. Ordinarily a valve with a large orifice is used to permit the oil to escape from the cylinder quickly, thereby resulting in a small dampening effect. The extension of the spring is significantly dampened by contrast. Accordingly, a much narrower orifice is typically used for a second valve, which opens when the piston travels in the other direction, corresponding to the extension of the telescoping members. The shock absorber is therefore double-acting, with different levels of dampening occurring in each of the two directions.
The most popular type of shock absorber is the telescoping shock absorber. The telescoping shock absorber is attached to opposite ends of a strut and comprises two tubes, one fitting inside the other. The piston rod is connected to the outer tube and moves in an oil-filled inner chamber within the inner tube. The tube contains flap valves which alternately allow oil to pass in one direction and produce the dampening action.
When the telescoping pistons contract, the oil is forced through a flap valve into an outer chamber. When the piston moves back (corresponding to the decompression of the strut), the oil flows from the outer chamber through a second valve and back into the main chamber. There has heretofore been no reliable dynamic method for controlling the degree of dampening and tension between the cylinders.
It has been recognized for several decades that certain fluids respond to the influence of an electric potential by evidencing a rapid and pronounced increase in viscosity and an increased resistance to shear. Such electro-rheological or electroviscous fluids comprise slurries of finely divided hydrophilic solids in hydrophobic liquids. In the absence of an electric field, these fluids behave in a Newtonian fashion, but when an electric field is applied, the fluids become proportionately more viscous as the potential of the electric field increases. In strong electric fields, the fluids can thicken into a solid. The electro-rheological phenomenon reverses when the electric potential is removed, and the material returns to its fluid state. Electro-rheological fluids change their state very rapidly when electric fields are applied or released, with typical response times being on the order of one millisecond. The ability of electro-rheological fluids to respond rapidly to electrical signals makes them well suited as elements in mechanical devices. Patents directed to compositions of electro-rheological fluids include U.S. Pat. Nos. 3,367,872; 3,047,507 and 4,033,892. Electro-rheological fluids have been extensively used in clutches as disclosed, for example, in U.S. Pat. Nos. 4,444,298 and 4,493,615.
Recently, there have been preliminary efforts directed toward using electro-rheological fluids in shock absorbers or other dampening devices. These early efforts have been costly, and have produced systems requiring large quantities of expensive electro-rheological fluids and large electrified sleeves. Such early efforts at electro-rheological shock absorbers have also typically required the inclusion of long fixed electrode plates.
It would be desirable to have an electro-rheological shock absorber which can be utilized with conventional shock absorber designs currently in operation.
It would further be desirable to have an electro-rheological shock absorber which utilizes novel electrode configurations.
It would further be desirable to have an electro-rheological shock absorber which can replace the expensive and complex flap valving currently in use in conventional shock absorbers.
It would further be desirable to provide a novel shock absorber and dampening mechanism which can be easily utilized in a variety of vehicles.
In view of the above, it is an object of the present invention to provide a novel electro-rheological shock absorber which can replace conventional hydraulic shock absorbers.
It is a further object of the present invention to provide an electro-rheological shock absorber having a novel electrode configuration situated within the device itself which facilitates compactness, control, and which further facilitates compatibility with the on-board computers, microprocessors and state-of-the-art electronics found in today's automobiles and trucks.
Still another object of this invention is to provide the advantages of electro-rheological control with minimum quantity of the electro-rheological fluid.
Another object of this invention is to incorporate the electro-rheological control means in conventional shock absorbers without major manufacturing modifications.
An additional object of this invention is to provide an electro-rheological shock absorber which provides smoother operation at all speeds and driving conditions.
A still further object of the invention is to provide an electro-rheological shock absorber which is self-contained and which can easily be removed and replaced as a single unit.